Trailer Ball Size Chart

How to use this chart

1. Read the size off the coupler, not off the ball. Every trailer coupler has its size stamped or cast into it, usually on the top or the side of the socket. That number is the answer to "what size ball do I need" and nothing else is.
2. Type what the trailer weighs loaded. Trailer plus cargo plus fuel plus water. A scale ticket if you have one, the GVWR off the trailer's own plate if you do not. This is what turns a reference table into a recommendation.
3. Measure the hole in your ball mount. Optional, and the most useful thing on the page. It is the step that catches a setup where the ball you need physically will not bolt to the mount you own.
4. Already own a ball and don't know what it is? Measure it. Open the measure panel and enter the diameter at its widest point. If it lands between 1-7/8 and 2 inches the tool refuses to guess, which is the correct answer at that width.
5. Take it with you. Share copies a link that reopens on your exact numbers. The PDF is two landscape pages with the whole chart, the part table and the torque figures, for the toolbox or the build thread.

Why this chart is different

Search this and every result hands you the same four-row table: 1-7/8 inch is 2,000 to 3,500 pounds, 2 inch is 3,500 to 12,000, 2-5/16 inch is 6,000 to 30,000. That is a range, not an answer. Nobody buys a ball for "6,000 to 30,000 pounds". They buy one for a 9,400 lb horse trailer, and the range does not tell them whether the ball in their hand covers it.

• Capacity by part, not by diameter. Fifteen published trailer balls with what each one is actually rated for. This is the table the ranges are hiding, and it is the only way to answer the question people are really asking.
• It checks the hole in your ball mount. A 2-5/16 inch ball on a 1 inch shank is published at 7,500 lb. If you need 9,000, no 1 inch shank in that diameter will do it and the part to change is the ball mount. No other chart on this subject models the mount at all.
• Ball nut torque, which nothing else on page one prints. 160 ft-lb on a 3/4 inch shank, 250 on a 1 inch, 450 on a 1-1/4 inch. Each figure held on every single part in the table that carries that shank. A hitch ball that backs off is a hitch ball that was never torqued.
• The mounting rule, also missing everywhere else. The platform has to be at least 3/8 inch thick and the hole must not be more than 1/16 inch wider than the shank. Both halves appear in the manufacturer's own notes and on none of the size charts competing for this search.
• It says where the published sources disagree. One page-one result puts the gap between 1-7/8 and 2 inch balls at 1/16 inch. It is 1/8 inch. Another lists three standard sizes; there are four. A third caps 2-5/16 inch at 21,000 lb where the manufacturer publishes 30,000.
• Printable and embeddable. Two-page PDF, one line of HTML for the embed, free, with attribution built in.

How trailer ball sizing actually works

Three measurements have to be right and they are independent of each other. The ball diameter has to match the coupler exactly. The shank diameter has to match the hole drilled through your ball mount. The rated capacity has to exceed your loaded trailer weight. Get two right and the third wrong and you have a problem that looks like it is working right up until it is not.

The word "shank" is doing double duty in this subject and it causes real confusion. On a trailer ball it is the threaded stem underneath, measured in 3/4, 1 and 1-1/4 inch. On a ball mount it is the square bar that slides into your receiver, measured in 1-1/4, 2, 2-1/2 and 3 inch. Same word, different part, different number. This page only ever means the threaded stem.

Why you cannot read capacity off the dimensions

This is the part every other chart skips, and it is the whole reason the ranges are so wide. Capacity comes from the forging, the steel grade and the heat treatment. It is not geometry. You cannot see it, you cannot measure it, and you cannot infer it, any more than you can tell a grade 5 bolt from a grade 8 without reading the head markings.

Three published parts make the point better than any explanation. Two 2-5/16 inch balls from the same manufacturer, both on an identical 1-1/4 inch by 2-5/8 inch shank, are rated 10,000 lb and 30,000 lb. Three times the capacity, same maker, no dimensional difference at all. Elsewhere in the same catalogue, a 2-5/16 inch ball on a 1 inch shank out-rates a 2-5/16 inch ball on a 1-1/4 inch shank. And a 2 inch ball is published higher than every 2-5/16 inch ball in the range but one.

So the rule is short: read the number stamped on the ball. That is not a disclaimer, it is the actual method. Everything in the table above is here so you know what is available and what to look for, and the stamp is what governs your trailer.

Torque, and why it is the step that gets skipped

A trailer ball does not usually fail by breaking. It fails by working loose, over a few hundred miles, as an under-tightened nut gives up a little at a time. Then the ball rotates in the mount, the coupler starts to chatter over bumps, and eventually the connection is gone.

Torque follows the thread, not the ball: 160 ft-lb for a 3/4 inch shank, 250 for a 1 inch, 450 for a 1-1/4 inch. That last figure is worth pausing on, because 450 ft-lb is past where most half-inch-drive click wrenches stop. If you are fitting a heavy ball you need three-quarter-inch drive or a multiplier, and the nut takes a 1-7/8 inch socket that is not in a normal set. Our roundup of the best torque wrenches covers which ones hold accuracy at the top of their range, which is exactly where this job lives, and the socket set guide covers which sets actually go past 1-1/2 inch.

Re-check it. Once after the first hundred miles, and again at the start of every towing season. A torque wrench is the only way to know, and this is one of the few fasteners on a trailer where the consequence of guessing is the trailer coming off.

The weakest link sets your capacity

Five parts carry the load and the lowest-rated one decides everything: the tow vehicle, the hitch receiver, the ball mount, the ball, and the coupler on the trailer. A 30,000 lb ball on a 5,000 lb ball mount is a 5,000 lb setup. This is worth saying because hitch "class" invites the opposite assumption. Class is a rough sorting convention, not a single published standard, and SAE J684 assigns different figures to the same class numbers than the ranges retailers print. Class gets you to the right aisle. The stamped rating on each part is the specification.

Worked examples

Utility trailer, 2 inch coupler, 3,000 lb loaded. The lowest published 2 inch rating that clears is 3,500 lb, and it comes on a 3/4 inch shank. That is 500 lb of headroom, about 17%. The nut torques to 160 ft-lb, which an ordinary half-inch click wrench reaches comfortably. Expect 300 to 450 lb on the tongue.

Travel trailer, 2 inch coupler, 9,000 lb loaded, 1 inch hole in the ball mount. A 2 inch ball can do this: there is a published part at 12,000 lb on a 1 inch shank, so your existing mount is fine and the nut wants 250 ft-lb. Note what would have happened on the diameter range alone: "3,500 to 12,000 lb" is true and tells you nothing about whether your 1 inch hole works. It does, but only because one specific part happens to be rated that high.

Horse trailer, 2-5/16 inch coupler, 8,000 lb loaded, 1 inch hole in the ball mount. This is the case worth reading twice. Every published 2-5/16 inch ball on a 1 inch shank tops out at 7,500 lb. You are 500 lb over on a part that looks perfectly reasonable in the catalogue. The parts that clear 8,000 lb all run a 1-1/4 inch shank, which will not go through your mount. The ball mount is what has to change, and drilling out a hitch platform is not a repair.

Small boat trailer, 1-7/8 inch coupler, 4,000 lb loaded. Nothing fits. The 1-7/8 inch size tops out at 3,500 lb published, and no amount of shopping changes that. You need a 2 inch setup, which means a new coupler on the trailer as well as a new ball, because the coupler has to match the ball. This is the answer people do not want and it is the right one.

Frequently asked questions

How do I know what size trailer ball I need?

Read the size stamped on the trailer's coupler. It will say 1-7/8, 2, 2-5/16 or 3 inches, and the ball has to match it exactly. Then check two more things: that the ball's rated capacity exceeds your loaded trailer weight, and that its threaded shank fits the hole in your ball mount. All three have to be right. Weight alone does not pick the diameter, because a light trailer can still be built with a big coupler.

Are most trailers a 2 inch ball?

The 2 inch ball is the most common size on the road, mostly because it pairs with Class 3 hitches and Class 3 is the most popular hitch. But "most common" is not "universal", and treating it as universal is how people end up with a 1-7/8 inch coupler and a 2 inch ball in the same toolbox. Check the stamp every time you hook to a trailer you have not towed before.

Can I use a 1-7/8 inch ball with a 2 inch coupler?

No. The ball would be an eighth of an inch undersized in the socket, which means the latch can close on it while the ball still has room to move. That connection comes apart over a bump or under braking, and it does so without warning. Undersized is the more dangerous direction of the two mismatches, because it latches and therefore looks correct.

Can I tow a 2-5/16 inch coupler with a 2 inch ball?

Also no, and for the same reason with more slop. A 2-5/16 inch coupler needs a 2-5/16 inch ball. If you regularly tow both, the fix is a switch-ball or multi-ball mount that carries two or three diameters, not a single ball you hope will span them.

What size ball do most pop-up campers use?

Usually 2 inch, occasionally 1-7/8 inch on the smallest and oldest ones. Pop-ups tend to sit between 1,500 and 3,000 lb loaded, which is inside what a 3/4 inch shank covers in either diameter. Still read the coupler, because pop-ups are frequently sold on and re-tongued.

What does the shank diameter actually change?

Two things: whether the ball bolts to your mount at all, and what you torque the nut to. It does not reliably tell you the capacity. In the published parts on this page a 1 inch shank reaches 12,000 lb in a 2 inch ball, while a 1-1/4 inch shank in a 2-5/16 inch ball sits at 6,000 lb. Bigger shank, lower rating. Match the shank to the hole, then read the stamp for the rating.

Related tools

• Towing Capacity Calculator — the other half of the question: what your truck can pull, before the trailer's hardware is even in the picture.
• Towing Capacity by VIN — decode your own VIN for a tow rating, free, with no dealer signup.
• Trailer Tire Load Range Chart — what the trailer's tires carry, which is the next thing in the chain that runs out of capacity.
• Bolt & Lug-Nut Torque Calculator — for everything on the trailer that is not the ball nut.
• Ft-Lbs to Nm Converter — if your wrench reads in newton-metres, 450 ft-lb is a number worth converting carefully.
• Browse all free tools by Mike Reeves →

Mike's recommendations for hitch ball work

Three things make the difference between a ball that is fitted and a ball that is torqued:

• Best Torque Wrenches — the ball nut is a 160 to 450 ft-lb fastener depending on the shank, and the top of that range is past a lot of half-inch-drive wrenches. Check the rated range before you find out in a driveway.
• Best Socket Sets — ball nuts run 1-1/8 to 1-7/8 inch across the flats. A standard set stops well short, and a 12-point on a nut at 450 ft-lb is how you round it off.
• Best Truck Bed Tool Boxes — if you tow more than one trailer you own more than one ball, plus pins and locks. A box that latches beats a bed that rolls them into the tailgate.

Sources & methodology

• CURT Manufacturing — Standard Trailer Hitch Ball Sizes — the four standard diameters with shank length, shank diameter and GTW ranges, plus the definitions of ball diameter, shank length, shank diameter and rise. The spine of the summary table.
• CURT part pages (individual SKUs) — every capacity, shank dimension, rise and torque figure in the part table was read from that part's own published specification block. Eleven of the fifteen were read in full; the remaining four are from the manufacturer's own part title and description, and are flagged as such in the data file so their torque is never presented as a per-part figure.
• AutoZone — What Size Hitch Ball Do I Need? and The Trailer Parts Outlet — Hitch, Ball and Coupler Sizes — independent publications of the same diameter and shank ranges, used as cross-checks.
• Mechanical Elements — Trailer Hitch Class Ratings — the source for the point that SAE J684 assigns different GTW figures to the same class numbers than retailer charts do.

Nothing on this page is calculated from a dimension. Ball capacity is a property of the forging, the steel grade and the heat treatment, so every rating here is a published figure attached to a part number rather than an output of a formula. Where two published sources disagree, the manufacturer's own per-part specification wins and the disagreement is stated rather than quietly resolved. The torque-by-shank rule is not a rule of thumb: it was checked against all ten parts in the table whose full specification block was read, and held on every one.

The part catalogue, the selection logic and the measurement identifier are asserted by fixtures.test.mjs next to the tool's data file, and the test runs before the site can build. It proves the lookup is a filter over published parts that can never invent a rating, that the three documented capacity inversions are still present in the data, that every diameter and millimetre conversion is exact, that each verdict tier is reachable from a real input, and that every figure quoted in the prose above is still derivable from the table below it. About Mike Reeves · Last reviewed September 25, 2026.

Manufacturer specifications override everything here. The rating stamped on your ball, coupler, ball mount and receiver is the authority, not this chart and not the diameter. Verify in your owner's manual or the OEM service data before you tow.

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